HLA-DRB1 and hydrops fetalis: Two different haplotypes showed the highest 4-digit haplotype frequencies: HLA-A*01:01/HLA-B*08:01/HLA-C*07:01/HLA-DRB1*03:01 and HLA-A*02:01/HLA-B*18:01/HLAC*07:01/HLA-DRB1*11:04, which were detected in 27 (HF 3.33%) and 23 individuals (HF 2.84%), respectively (Table 3, Figure 2).